Hypoglycemia

Hypoglycemia occurs when the blood sugar level is too low, and it can cause symptoms such as weakness, dizziness, shaking, sweating, blurred vision, facial tingling, and possibly even loss of consciousness or death. People with type 1 diabetes are at greater risk for hypoglycemia than are those with type 2 diabetes.

Exercise-related hypoglycemia is the primary risk in the active person with diabetes. To understand this better, first let's take a look at what happens to glucose metabolism in the exercising person who does not have diabetes. The blood glucose will be at a normal level before the person starts to exercise; once that person begins exercising, the body increases the availability of blood glucose as it is being used for fuel, keeping it within a normal range. Many mechanisms enable the body to maintain normal glucose levels, but there are two main mechanisms that you should be aware of. The first is the body's sensing mechanism that reduces insulin in the blood and increases glucose availability. The second is the ability of the liver and muscles to produce glucose.

The body's sensing mechanism allows it to monitor glucose levels very carefully. And when the blood glucose reaches lower levels than the body cannot tolerate, it activates certain regulatory hormones that induce the breakdown process of stored glucose and new production of sugar in the liver. However, in a person with type 1 diabetes, the only insulin that can be regulated is that taken by the patient. And the insulin that the person takes, typically in the form of a subcutaneous injection, will continue to be absorbed, which can lead to higher-than-adequate levels of insulin in the blood, increasing the chance of hypoglycemia.

Some with type 1 diabetes may have an impaired glucose regulating system, making it difficult for them to increase their glucose levels by these most critical glucose-regulating mechanisms. Simply put, if a person with type 1 diabetes is exercising, he needs to have enough, but not too much, insulin present in the body and enough glucose in the blood.

One way to reduce the risk of hypoglycemia in those who use insulin is to ensure that the insulin is injected into subcutaneous tissues of the abdomen. Insulin should not be placed in the extremities (the arms or legs). This is the main cause of hypoglycemia in active insulin-dependent diabetes. Not only is insulin less reliable if placed in an extremity, it also is absorbed at a much faster rate during exercise, which leads to increased levels of insulin in the blood. This quickly decreases the blood glucose levels, creating a hypoglycemic state.

Another approach to avoiding hypoglycemia is to make sure that you consult your physician, who will help you adjust your insulin or hypoglycemic agent and your diet before you start an exercise program. This will be an ongoing process, with most of the changes occurring in the first few months. Your physician will look at your current insulin or hypoglycemic agent dose (if you are currently taking the medications) and look at your recorded log of insulin levels over the last few months. In addition, your doctor will likely look at your hemoglobin A1C levels to get an idea of how well your glucose has been controlled. Once your doctor determines that your glucose levels have been adequately controlled, she will likely have you start exercising gradually (such as walking 10 to 20 minutes) monitoring your glucose just before exercise, during exercise, just after exercise, and sometimes hours later. The reason for checking your glucose often is to ensure that your glucose level is maintained during exercise. This is the overall goal of monitoring your glucose when you start an exercise program.

Note that those with type 2 diabetes who are not insulin dependent rarely have encounters with hypoglycemia. When it does occur, it is usually associated with the use of sulfonylureas, a certain type of hypoglycemic agent. Moreover, hypoglycemia is most likely to occur after you exercise in the evening rather than in the morning. This is due to glucose-regulating hormone level variations that occur in response to the time of day, referred to as diurnal variation.